Symbiotic effectiveness of inoculation with Bradyrhizobium isolates on soybean [Glycine max (L.) Merrill] genotypes with different maturities

The influence of soybean genotypes with different maturity groups on the symbiotic effectiveness of Bradyrhizobium spp under high native soil N is not well known. Therefore, the objective of this work was to evaluate the influence of maturity time of soybean genotypes on the symbiotic effectiveness of Bradyrhizobium spp. at higher soil N. Three isolates of Bradyrhizobium spp. (UK-isolate, TAL-379 isolate and local-isolate) and six soybean genotypes, three late maturing (Wogayen, TGx-1336424 and Belsa) and three medium maturing (GIZA, Afgat and Gishame) were used for greenhouse experiment. Only GIZA and TGx-1336424 were selected for field experiment. The result of the experiments showed that significantly (P < 0.05) differences in all investigated traits, except total plant tissue N, was observed in TGx-1336424 with UK-Isolate and Local-Isolate.TAL-379 inoculation performed better in all investigated traits of GIZA genotype than other inoculation treatments. N-fertilization in the greenhouse experiment significantly (P < 0.05) improved the shoot biomass of Wogayen and Belsa-95, but did not observe in GIZA and Gishame. The regression analysis obtained between nodule number and nodule dry weight with that of grain yield indicated generally higher R(2) value for late maturing than that of the medium maturing genotypes. This indicates high importance of nodulation for improving the GY of late maturing genotypes. Hence, this study proves the need for inoculation to improve the production and productivity of soybean sustainably in Ethiopia, with particularly pronounced effect on late maturing genotypes of soybean.